North Korea appears close to finishing a new missile launch site, according to analysis of satellite images taken in the last month, which show an almost completed 100ft tall launch tower, suggesting a step forward in Pyongyang's inter-continental ballistic missile programme.

"I think its fair to say that the tower is basically operational," said Tim Brown, the globalsecurity.org image analyst who identified the development. "I do not see the North Korean missile programme as a real military threat. It is just enough of a programme to get political attention and be used as a bargaining chip. It is one way they can go to the six-party talks and have something real to negotiate with.

"Talks on aid for denuclearisation, which North Korea walked out of in 2009, remain stalled following its attack on Yeonpyeong island and the sinking of a South Korean warship. Although the country already has one launch site, at Musudan-ri, Tongchang-dong appears far more sophisticated. Brown and a colleague were the first to publicly reveal the facility, in 2008.

He told Voice of America that Pyongyang had been developing the site, in the north-west of the country, for around 10 years.

"The other [site], it had dirt roads; it was pretty primitive. This one looks to be more of a serious site with support facilities that are needed to sustain a program – what you'd want to do if you are serious about testing long-range missiles," Daniel Pinkston, Seoul-based analyst for the International Crisis Group, told the Washington Post

But Michael Ellemann, a proliferation expert at the International Institute for Strategic Studies, noted: "[It is] not clear why [North Korea] is building it, as the existing facilities at Musudan-ri are adequate and better located for space launches, or missiles against US or Japanese targets."

He added that although it might be used in the near future, given how close it was to completion, it was unclear what it would be used for.

But proliferation experts were sceptical, noting that although Pyongyang has been attempting to create a long-range missile for years, its tests have been sporadic and largely unsuccessful.

David Santoro, also of the International Institute for Strategic Studies, noted: "Much more important [than this site] is the missile itself. And in this regard, North Korea does not have the technology to strike the United States, nor will it have it anytime soon, despite what Robert Gates suggested last month. The ICBM tests it conducted in 2006 and 2009 were quite revealing in this regard."

Brown also noted the failures of the missile tests, but added that the North was likely to be benefiting from Iran's "much more successful" and better-funded research.